Zinc or zinc alloy electroplating method and system

ABSTRACT

The present invention provides a zinc or zinc alloy electroplating method comprising: performing energizing in an alkaline zinc or zinc alloy electroplating bath provided with a cathode and an anode, wherein the anode is an anode in which a conductive substrate is coated in a conductive state with alkali-resistant ceramics, the alkaline zinc or zinc alloy electroplating bath is an alkaline zinc plating bath containing an organic compound additive or an alkaline zinc alloy electroplating bath containing an amine chelating agent or an organic compound additive, oxidation decomposition, on a surface of the anode caused by the energizing, of the organic compound additive in the alkaline zinc plating bath or the amine chelating agent and the organic compound additive in the alkaline zinc alloy electroplating bath is suppressed as compared with a case of using as an anode the same conductive substrate uncoated with the alkali-resistant ceramics.

TECHNICAL FIELD

The present invention relates to a zinc or zinc alloy electroplatingmethod and system, and in particular to an electroplating method andsystem for applying zinc or zinc alloy electroplating excellent incorrosion resistance to a steel member or the like by using an alkalinezinc or zinc alloy electroplating bath, in which the use of an anode inwhich a conductive substrate is coated in a conductive state withalkali-resistant ceramics enables long-term use of the electroplatingbath while maintaining plating bath performance.

BACKGROUND ART

Zinc plating has been used as inexpensive rust-inhibitory plating whichuses a cyan compound-containing bath and contains almost no organiccompound. However, studies have been made in recent years on a zincplating bath which uses no highly toxic cyan compound, and zinc platingbaths containing organic compounds such as quaternary amine polymershave been prevailing. It is to be noted that the decomposition anddisappearance of these organic compounds by anodic oxidation result indendrite deposition with poor adhesion, making it impossible to carryout good zinc rust-inhibitory plating.

Zinc alloy plating has corrosion resistance superior to that of zincplating and thus is widely used for automotive components and the like.In particular, alkaline zinc nickel alloy plating baths are used forfuel parts requiring high corrosion resistance and engine parts placedin a high temperature environment. An alkaline zinc nickel alloy platingbath is a plating bath in which an amine chelating agent suitable for aNi co-deposition ratio is selected to dissolve nickel, and zinc andnickel are co-deposited as a plating film. However, electroplating byuse of an alkaline zinc nickel alloy plating bath encounters a problemof oxidation decomposition of the amine chelating agent on the anodesurface during the energizing. In the coexistence of nickel ions andferrous metal ions such as iron ions, they act as oxidation catalysts tofurther promote the oxidation decomposition of the amine chelatingagent. Therefore, when the alkaline zinc nickel alloy plating bath comesinto contact with the anode, the amine chelating agent rapidlydecomposes, which rapidly decreases the plating performance. Theaccumulation of decomposed products causes a number of problems such asdecrease in electric current efficiency, increase in bath voltage,decrease in plating film thickness, decrease in nickel content in theplating film, reduction in current density range in which plating ispossible, reduction in gloss, and increase in COD. Therefore, it isimpossible to use a plating bath for a long time, requiring thereplacement of the plating bath.

Several methods have been so far known as remedies against the above.For example, Published Japanese Translation of PCT InternationalApplication No. 2002-521572 discloses a method in which an alkaline zincnickel alloy plating bath (catholyte) and an acidic anolyte areseparated with a positive ion exchange membrane composed ofperfluoropolymer. However, in the case of using an acidic solution asthe anolyte, an expensive corrosion-resistant member such asplatinum-plated titanium has to be used as the anode. In addition, whenthe separating membrane is broken, an accident may occur in which theacidic solution on the anode side and the alkaline solution on thecathode side mix to cause a sudden chemical reaction. On the other hand,in the case of using an alkaline liquid as the anolyte in place of anacidic liquid, the present inventors conducted a plating test andrevealed that the anolyte rapidly transferred to the catholyte due toenergizing, causing lowering of the liquid surface level of the anolyteand rising of the liquid surface level of the catholyte at the sametime.

As a method of solving the problems above, Japanese Patent ApplicationPublication No. 2007-2274 describes a method of replenishing an alkalinecomponent to the alkaline anolyte by using a cation exchange membrane.However, this method requires additional equipment, liquid management,and the like, making the operations complicated.

In addition, International Publication No. WO2016/075963 describes amethod of zinc alloy electroplating, including separating the cathoderegion including the cathode and the anode region including the anodewith a negative ion exchange membrane, using an alkaline zinc alloyplating solution as the catholyte included in the cathode region, andusing an alkaline aqueous solution as the anolyte included in the anoderegion. This method suppresses the oxidation decomposition of the aminechelating agent on the anode in the bath but has a problem that negativeions transfer from the plating solution to the anode electrolyte, andsodium carbonate, sodium sulfate, and sodium oxalate rapidly increaseand are deposited and precipitated on the film to destroy the film. Toprevent this, it is necessary to control the concentration of impuritiesin the anolyte and to renew the anolyte frequently. In addition, theintroduction of an anode cell is not economical because it requires avery expensive facility investment, a large installation site for ananolyte circulation tank, piping, and others, maintenance of the anodecell, regular membrane replacement, and so forth.

Moreover, Published Japanese Translation of PCT InternationalApplication No. 2008-539329 discloses a zinc alloy plating bath in whicha cathode and an anode are separated with a filtration membrane.However, the present inventors examined it and revealed that thedisclosed filtration membrane was not able to prevent the transfer ofthe catholyte and the anolyte and was not able to prevent thedecomposition of the chelating agent on the anode. In addition, sincethe zinc alloy plating solution is also used as the anolyte, thedecomposition of the anolyte is greatly promoted, which thus requiresreplacement of the anolyte. Without the replacement, the decomposedproducts transfer into the plating solution of the cathode. Therefore,the liquid lifetime was found not to be extended substantially.

SUMMARY OF INVENTION

An object of the present invention is to provide an inexpensive andeconomical plating method capable of achieving lifetime extension of azinc or zinc alloy plating bath while maintaining the performancethereof, the method suppressing the oxidation decomposition of achelating agent or a brightening agent on the anode surface withoutusing a special apparatus such as an expensive anode cell.

The present invention has been made based on the knowledge that use ofan anode in which a conductive substrate is coated in a conductive statewith alkali-resistant ceramics maintains the plating bath performancebecause oxidation decomposition of the amine chelating agent does nottake place on the anode surface in the bath. Specifically, the presentinvention provides a zinc or zinc alloy electroplating method and systemdescribed below.

[1]

A zinc or zinc alloy electroplating method comprising:

performing energizing in an alkaline zinc or zinc alloy electroplatingbath provided with a cathode and an anode, wherein

the anode is an anode in which a conductive substrate is coated in aconductive state with alkali-resistant ceramics,

the alkaline zinc or zinc alloy electroplating bath is an alkaline zincplating bath containing an organic compound additive or an alkaline zincalloy electroplating bath containing an amine chelating agent or anorganic compound additive,

oxidation decomposition, on a surface of the anode caused by theenergizing, of the organic compound additive in the alkaline zincplating bath or the amine chelating agent and the organic compoundadditive in the alkaline zinc alloy electroplating bath is suppressed ascompared with a case of using as an anode the same conductive substrateuncoated with the alkali-resistant ceramics.

[2]

The zinc or zinc alloy electroplating method according to [1] describedabove, wherein

the anode in which a conductive substrate is coated in a conductivestate with alkali-resistant ceramics consists of a conductive substrateand an alkali-resistant ceramics coating.

[3]

The zinc or zinc alloy electroplating method according to [1] or [2]described above, wherein

the conductive substrate contains at least one of nickel and iron.

[4]

The zinc or zinc alloy electroplating method according to any one of [1]to [3] described above, wherein

the alkali-resistant ceramics contains at least one selected from thegroup consisting of tantalum oxide, aluminum oxide, tantalum nitride,aluminum nitride, silicon nitride, boron nitride, silicon carbide, andboron carbide.

[5]

The zinc or zinc alloy electroplating method according to any one of [1]to [4] described above, wherein

the alkaline zinc or zinc alloy electroplating bath is an alkaline zincelectroplating bath at least containing zinc ions, caustic alkali, andan organic compound additive.

[6]

The zinc or zinc alloy electroplating method according to any one of [1]to [4] described above, wherein

the alkaline zinc or zinc alloy electroplating bath is an alkaline zincalloy electroplating bath at least containing zinc ions, metal ions,caustic alkali, an amine chelating agent, and an organic compoundadditive, and

the metal ions include at least one selected from the group consistingof nickel ions, iron ions, cobalt ions, tin ions, and manganese ions.

[7]

The zinc or zinc alloy electroplating method according to [6] describedabove, wherein

the amine chelating agent contains at least one selected from the groupconsisting of alkylene amine compounds, alkylene oxide adducts thereof,and alkanolamine compounds.

[8]

A zinc or zinc alloy electroplating system comprising:

an alkaline zinc or zinc alloy electroplating bath provided with acathode and an anode, wherein

the anode is an anode in which a conductive substrate is coated in aconductive state with alkali-resistant ceramics,

the alkaline zinc or zinc alloy electroplating bath is an alkaline zincplating bath containing an organic compound additive or an alkaline zincalloy electroplating bath containing an amine chelating agent or anorganic compound additive,

oxidation decomposition, on a surface of the anode caused by theenergizing, of the organic compound additive in the alkaline zincplating bath or the amine chelating agent and the organic compoundadditive in the alkaline zinc alloy electroplating bath is suppressed ascompared with a case of using as an anode the same conductive substrateuncoated with the alkali-resistant ceramics.

[9]

The zinc or zinc alloy electroplating system according to [8] describedabove, wherein

the anode in which a conductive substrate is coated in a conductivestate with alkali-resistant ceramics consists of a conductive substrateand an alkali-resistant ceramics coating.

[10]

The zinc or zinc alloy electroplating system according to [8] or [9]described above, wherein

the conductive substrate contains at least one of nickel and iron.

[11]

The zinc or zinc alloy electroplating system according to any one of [8]to [10] described above, wherein

the alkali-resistant ceramics contains at least one selected from thegroup consisting of tantalum oxide, aluminum oxide, tantalum nitride,aluminum nitride, silicon nitride, boron nitride, silicon carbide, andboron carbide.

[12]

The zinc or zinc alloy electroplating system according to any one of [8]to [11] described above, wherein

the alkaline zinc or zinc alloy electroplating bath is an alkaline zincelectroplating bath at least containing zinc ions, caustic alkali, andan organic compound additive.

[13]

The zinc or zinc alloy electroplating system according to any one of [8]to [11] described above, wherein

the alkaline zinc or zinc alloy electroplating bath is an alkaline zincalloy electroplating bath at least containing zinc ions, metal ions,caustic alkali, an amine chelating agent, and an organic compoundadditive, and

the metal ions include at least one selected from the group consistingof nickel ions, iron ions, cobalt ions, tin ions, and manganese ions.

[14]

The zinc or zinc alloy electroplating system according to [13] describedabove, wherein

the amine chelating agent contains at least one selected from the groupconsisting of alkylene amine compounds, alkylene oxide adducts thereof,and alkanolamine compounds.

The present invention makes it possible to provide an economical platingmethod and system capable of achieving lifetime extension whilemaintaining zinc or zinc alloy electroplating bath performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates the results (plating appearance) of a plating test inaccordance with a hull cell test of Example 1.

FIG. 2 illustrates the results (plating appearance) of a plating test inaccordance with a hull cell test of Example 2.

FIG. 3 illustrates the results (plating appearance) of a plating test inaccordance with a hull cell test of Example 3.

FIG. 4 illustrates the results (plating appearance) of a plating test inaccordance with a hull cell test of Comparative Example 1.

FIG. 5 illustrates the results (plating appearance) of a plating test inaccordance with a hull cell test of Comparative Example 2.

FIG. 6 illustrates the results (film thickness distribution) of aplating test in accordance with a hull cell test of Example 1.

FIG. 7 illustrates the results (Ni co-deposition ratio distribution) ofa plating test in accordance with a hull cell test of Example 1.

FIG. 8 illustrates the results (film thickness distribution) of aplating test in accordance with a hull cell test of Example 2.

FIG. 9 illustrates the results (Ni co-deposition ratio distribution) ofa plating test in accordance with a hull cell test of Example 2.

FIG. 10 illustrates the results (film thickness distribution) of aplating test in accordance with a hull cell test of Example 3.

FIG. 11 illustrates the results (Ni co-deposition ratio distribution) ofa plating test in accordance with a hull cell test of Example 3.

FIG. 12 illustrates the results (film thickness distribution) of aplating test in accordance with a hull cell test of Comparative Example1.

FIG. 13 illustrates the results (Ni co-deposition ratio distribution) ofa plating test in accordance with a hull cell test of ComparativeExample 1.

FIG. 14 illustrates the results (film thickness distribution) of aplating test in accordance with a hull cell test of Comparative Example2.

FIG. 15 illustrates the results (Ni co-deposition ratio distribution) ofa plating test in accordance with a hull cell test of ComparativeExample 2.

DESCRIPTION OF EMBODIMENTS

A zinc or zinc alloy electroplating method of the present inventionincludes performing energizing in an alkaline zinc alloy electroplatingbath provided with a cathode and an anode.

Examples of the metal combined with zinc as zinc alloy plating includeone or more metals selected from nickel, iron, cobalt, tin, andmanganese. Specific examples include, but are not limited to, zincnickel alloy plating, zinc iron alloy plating, zinc cobalt alloyplating, zinc manganese alloy plating, zinc tin alloy plating, and zincnickel cobalt alloy plating. The zinc alloy plating is preferably zincnickel alloy plating.

The cathode is a plateable object to be subjected to zinc or zinc alloyelectroplating. Examples of the plateable object include objects ofvarious shapes such as plate-shaped objects, rectangularparallelepipeds, cylinders, hollow cylinders, and spherical objects ofvarious metals including iron, nickel, and copper, alloys thereof, andmetals and alloys including aluminum subjected to zinc substitutiontreatment.

The anode used is an anode in which a conductive substrate is coated ina conductive state with alkali-resistant ceramics. Examples of thealkali-resistant ceramics include, but are not limited to, tantalumoxide, aluminum oxide, tantalum nitride, aluminum nitride, siliconnitride, boron nitride, silicon carbide, and boron carbide. Thealkali-resistant ceramics preferably contains at least one selected fromthe group consisting of tantalum oxide, aluminum oxide, tantalumnitride, aluminum nitride, silicon nitride, boron nitride, siliconcarbide, and boron carbide. The preparation of a coating film of thealkali-resistant ceramics on a conductive substrate is possible with,but not limited to, a combination of sintering and vapor phase platingor of vapor phase plating and anodic oxidation. In addition, theconductive substrate can be subjected to suitable pretreatment such asetching for the purpose of obtaining adhesion by the anchor effect. Inthis case, the arithmetic average roughness (Ra) of the surface ispreferably 3 to 4 μm, for example. Note that the top of the coating filmof the alkali-resistant ceramics may be coated with an ion exchangeresin or the like.

The film thickness of the coating film of the alkali-resistant ceramicsis preferably approximately 0.1 to 50 μm and particularly preferably 0.5to 1 μm. The conductivity decreases when the film thickness is toothick, and the decomposition suppression effect decreases when the filmthickness is too thin. The above preparation method may be carried outmore than once to set the total film thickness of the coating film ofthe alkali-resistant ceramics in the above ranges. The pore diameter inthe coating film of the alkali-resistant ceramics is preferablyapproximately 0.1 to 5 μm and further preferably 0.1 to 1 μm. Thedecomposition suppression effect decreases when the pore diameterexceeds 5 μm. Here, the conductive state means a state where ions andthe like can transfer through the above-described pores, cracks, and thelike.

The conductive substrate is preferably one coated with iron, nickel,stainless steel, carbon, titanium, zirconium, niobium, tantalum,platinum, platinum-plated titanium, palladium-tin alloy, or these, butis not limited to the above as long as the conductive substrate isconductive. The conductive substrate is more preferably contains atleast one of nickel and iron.

The anode in which a conductive substrate is coated in a conductivestate with alkali-resistant ceramics is preferably an anode composed ofa conductive substrate and an alkali-resistant ceramics coating.

The alkaline zinc electroplating bath used in the present invention isan alkaline zinc plating bath containing an organic compound additive.The alkaline zinc electroplating bath preferably contains one or moreorganic compound additives selected from the group consisting ofbrightening agents, auxiliary additives such as leveling agents, anddefoamers. The alkaline zinc electroplating bath is preferably onecontaining a brightening agent.

The alkaline zinc alloy electroplating bath used in the presentinvention is an alkaline zinc alloy electroplating bath containing anamine chelating agent and an organic compound additive. The alkalinezinc alloy electroplating bath preferably contains an amine chelatingagent and one or more organic compound additives selected from the groupconsisting of brightening agents, auxiliary additives such as levelingagents, and defoamers. The alkaline zinc alloy electroplating bathpreferably contains a brightening agent.

No particular limitation is imposed on the brightening agent as long asit is a brightening agent known in zinc plating baths, and examplesthereof include (1) nonionic surfactants such as polyoxyethylenepolyoxypropylene block polymers and acetylene glycol EO adducts andanionic surfactants such as polyoxyethylene lauryl ether sulfate andalkyl diphenyl ether disulfonate (2) polyamine compounds such as;polyallylamines such as copolymers of diallyldimethylammonium chlorideand sulfur dioxide; polyepoxy polyamines such as condensation polymersof ethylene diamine and epichlorohydrin, condensation polymers ofdimethylaminopropylamine and epichlorohydrin, condensation polymers ofimidazole and epichlorohydrin, condensation polymers of epichlorohydrinand imidazole derivatives such as 1-methylimidazole and2-methylimidazole, and condensation polymers of epichlorohydrin andheterocyclic amines containing triazine derivatives such asacetoguanamine and benzoguanamine polyamide polyamines includingpolyamine polyurea resins such as condensation polymers of3-dimethylaminopropyl urea and epichlorohydrin and condensation polymersof bis(N,N-dimethylaminopropyl)urea and epichlorohydrin andwater-soluble nylon resins such as condensation polymers ofN,N-dimethylaminopropylamine, alkylene dicarboxylic acids, andepichlorohydrin polyalkylene polyamines such as condensation polymers of2,2′-dichlorodiethyl ether with diethylenetriamine,dimethylaminopropylamine, and the like, condensation polymers ofdimethylaminopropylamine and 1,3-dichloropropane, condensation polymersof N,N,N′,N′-tetramethyl-1,3-diaminopropane and 1,4-di chlorobutane, andcondensation polymers of N,N,N′,N′-tetramethyl-1,3-diaminopropane and1,3-dichloropropan-2-ol (3) condensation polymers of dichloroethyl etherwith dimethylamine and the like (4) aromatic aldehydes such asveratraldehyde, vanillin, and anisaldehyde and benzoic acids or saltsthereof and (5) quaternary ammonium salts such as cetyltrimethylammoniumchloride, 3-carbamoylbenzyl chloride, and pyridinium. Among these,quaternary ammonium salts and aromatic aldehydes are preferable. Thesebrightening agents may be used alone or in combination of two or more.The concentration of the brightening agent in the alkaline zinc or zincalloy electroplating bath is preferably 1 to 500 mg/L and furtherpreferably 5 to 100 mg/L in the case of aromatic aldehydes and benzoicacids or salts thereof, and is preferably 0.01 to 10 g/L and furtherpreferably 0.02 to 5 g/L in other cases.

In addition, the brightening agent may be a nitrogen-containingheterocyclic quaternary ammonium salt. The nitrogen-containingheterocyclic quaternary ammonium salt brightening agent is morepreferably a carboxy group- and/or hydroxy group-substitutednitrogen-containing heterocyclic quaternary ammonium salt. Examples ofthe nitrogen-containing heteroring of the nitrogen-containingheterocyclic quaternary ammonium salt include pyridine rings, piperidinerings, imidazole rings, imidazoline rings, pyrrolidine rings, pyrazolerings, quinoline rings, and morpholine rings, and thenitrogen-containing heteroring is preferably a pyridine ring andparticularly preferably a quaternary ammonium salt of nicotinic acid ora derivative thereof. In the quaternary ammonium salt compound, thecarboxy group and/or hydroxy group may be a substituent in anitrogen-containing heteroring via a substituent as in the case of acarboxymethyl group. In addition, the nitrogen-containing heteroring mayhave a substituent such as an alkyl group other than the carboxy groupand/or hydroxy group. In addition, the N-substituent forming theheterocyclic quaternary ammonium cation is not particularly limited aslong as the brightening agent-containing effect is not inhibited, andexamples thereof include substituted or non-substituted alkyl groups,aryl groups, and alkoxy groups. In addition, examples of counter anionswhich form salts include compounds containing halogen anions, oxyanions, borate anions, sulfonate anions, phosphate anions, and imidoanions, and halogen anions are preferable. Such quaternary ammoniumsalts are preferable because they both contain quaternary ammoniumcations and oxyanions in the molecule and thus exhibit behavior asnegative ions. Specific examples of nitrogen-containing heterocyclicquaternary ammonium salt compounds include N-benzyl-3-carboxypyridiniumchloride, N-phenethyl-4-carboxypyridinium chloride,N-butyl-3-carboxypyridinium bromide, N-chloromethyl-3-carboxypyridiniumbromide, N-hexyl-6-hydroxy-3-carboxypyridinium chloride,N-hexyl-6-3-hydroxypropyl-3-carboxypyridinium chloride,N-2-hydroxyethyl-6-methoxy-3-carboxypyridinium chloride,N-methoxy-6-methyl-3-carboxypyridinium chloride,N-propyl-2-methyl-6-phenyl-3 -carboxypyridinium chloride,N-propyl-2-methyl-6-phenyl-3 -carboxypyridinium chloride,N-benzyl-3-carboxymethyl pyridinium chloride, 1-butyl-3-methyl-4-carboxyimidazolium bromide, 1-butyl-3-methyl-4-carboxymethyl imidazoliumbromide, 1-butyl-2-hydroxymethyl-3-methylimidazolium chloride,1-butyl-1-methyl-3 -methylcarboxypyrrolidinium chloride, and1-butyl-1-methyl-4-methylcarboxypiperidinium chloride. Thesenitrogen-containing heterocyclic quaternary ammonium salts may be usedalone or in combination or two or more. The concentration of thenitrogen-containing heterocyclic quaternary ammonium salt in thealkaline zinc or zinc alloy electroplating bath is preferably 0.01 to 10g/L and further preferably 0.02 to 5 g/L.

Examples of auxiliary additives include organic acids, silicates, andmercapto compounds. These auxiliary additives may be used alone or incombination of two or more. The concentration of the auxiliary additivein the alkaline zinc or zinc alloy electroplating bath is preferably0.01 to 50 g/L.

Examples of defoamers include surfactants. These defoamers may be usedalone or in combination or two or more. The concentration of thedefoamer in the alkaline zinc or zinc alloy electroplating bath ispreferably 0.01 to 5 g/L.

Examples of amine chelating agents include alkylene amine compounds suchas ethylenediamine, diethylenetriamine, tri ethylenetetramine,tetraethylenepentamine, and pentaethylenehexamine; alkylene oxideadducts such as ethylene oxide adducts and propylene oxide adducts ofthe above alkylene amines; aminoalcohols such as ethanolamine,diethanolamine, triethanolamine, diisopropanolamine,triisopropanolamine, ethylenediamine tetra-2-propanol,N-(2-aminoethyl)ethanolamine, and 2-hydroxyethylaminopropylamine;alkanolamine compounds such asN-(2-hydroxyethyl)-N,N′,N′-triethylethylenediamine,N,N′-di(2-hydroxyethyl)-N,N′-diethylethylenediamine,N,N,N′,N′-tetrakis(2-hydroxyethyl)propylenediamine, andN,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine; poly(alkylene imine)obtained from ethylene imine, 1,2-propylene imine, and the like; andpoly(alkylene amine) obtained from ethylene diamine, triethylenetetramine, and the like. The amine chelating agent preferably containsone or more selected from the group consisting of alkylene aminecompounds, alkylene oxide adducts thereof, and alkanolamine compound.These amine chelating agents may be used alone or in combination of twoor more. The concentration of the amine chelating agent in the alkalinezinc or zinc alloy electroplating bath is preferably 5 to 200 g/L andmore preferably 30 to 100 g/L.

The alkaline zinc or zinc alloy electroplating bath used in the presentinvention contains zinc ions. The concentration of the zinc ions in thealkaline zinc or zinc alloy electroplating bath is preferably 2 to 20g/L or more preferably 4 to 12 g/L. Examples of zinc ion sources includeNa₂[Zn(OH)₄], K₂[Zn(OH)₄], and ZnO. These zinc ion sources may be usedalone or in combination of two or more.

The alkaline zinc or zinc alloy electroplating bath used in the presentinvention preferably contains caustic alkali. Examples of causticalkalis include sodium hydroxide and potassium hydroxide, and sodiumhydroxide is preferable. The concentration of the caustic alkali in thealkaline zinc or zinc alloy electroplating bath is preferably 60 to 200g/L and more preferably 100 to 160 g/L.

The alkaline zinc alloy electroplating bath used in the presentinvention contains ions of metal other than zinc. As the above metalions, the alkaline zinc alloy electroplating bath preferably containsone or more kind of metal ions selected from the group consisting ofnickel ions, iron ions, cobalt ions, tin ions, and manganese ions. Thetotal concentration of the metal ions in the alkaline zinc alloyelectroplating bath is preferably 0.4 to 4 g/L and more preferably 1 to3 g/L. Examples of metal ion sources include nickel sulfate, ferroussulfate, cobalt sulfate, stannous sulfate, and manganese sulfate. Thesemetal ion sources may be used alone or in combination of two or more.The alkaline zinc alloy electroplating bath used in the presentinvention is preferably an alkaline zinc nickel alloy electroplatingbath containing nickel ions as the above metal ions.

The alkaline zinc electroplating bath is preferably an alkaline zincelectroplating bath at least containing zinc ions, caustic alkali, andan organic compound additive.

The alkaline zinc alloy electroplating bath is preferably an alkalinezinc alloy electroplating bath at least containing zinc ions, metalions, caustic alkali, an amine chelating agent, and an organic compoundadditive, and the metal ions include at least one kind selected from thegroup consisting of nickel ions, iron ions, cobalt ions, tin ions, andmanganese ions.

The temperature during the zinc or zinc alloy plating is preferably 15°C. to 40° C. and further preferably 25 to 35° C. The cathode currentdensity during the zinc or zinc alloy plating is preferably 0.1 to 20A/dm² and further preferably 0.2 to 10 A/dm².

Next, the present invention is described with reference to Examples andComparative Examples, but the invention is not limited to these.

EXAMPLES Example 1

An anode plate (surface roughness Ra: 4 μm, 64×64×2 mm) coated withtantalum oxide in a thickness of 0.5 to 0.8 μm on Ni was used and analkaline zinc nickel alloy plating bath shown below was used (500 mL) tocarry out zinc nickel alloy plating with energizing of 500 Ah/L. Thepore diameter in the coating film was 0.1 to 1 μm, and the drag-out ofthe plating bath was set to 2 mL/Ah. The cathode current density was 4A/dm², the anode current density was 9.8 A/dm², and the plating bathtemperature was 25° C. The plating bath was cooled to maintain 25° C. Aniron plate was used as the cathode. Note that the iron plate of thecathode was replaced for each 16 Ah/L during the energizing. The zincion concentration of the plating bath was kept constant by immersion anddissolution of the metal zinc. The nickel ion concentration of theplating bath was kept constant by replenishing a nickel replenishmentagent IZ-250YNi (manufactured by Dipsol). The caustic soda concentrationof the plating bath was periodically analyzed and replenished to aconstant concentration. The brightening agents replenished werepolyamine IZ-250YR1 (manufactured by Dipsol) and nitrogen-containingheterocyclic quaternary ammonium salt IZ-250YR2 (manufactured by Dipsol)at replenishing rates of 15 mL/kAh and 15 mL/kAh, respectively. Theamine chelating agent IZ-250YB was replenished at an IZ-250YBreplenishing rate of 80 mL/kAh. The concentration of the amine chelatingagent, the oxalic acid concentration, and the cyan concentration in thecatholyte were analyzed for each energizing of 250 Ah/L. In addition,the presence or absence of precipitate was visually observed. Table 1shows the results. Moreover, the chelating agent concentration was setto the initial concentration during the energizing of 500 Ah/L and along cell having a 20 cm iron plate as the cathode was used for aplating test in accordance with the hull cell test to measure theplating appearance, the film thickness distribution, and the Nico-deposition ratio distribution. FIG. 1, FIG. 6, and FIG. 7 show therespective results. Note that the conditions for the plating test inaccordance with the hull cell test were 4A-20 minutes and 25° C. Inaddition, the surface of the anode was observed to check the presence orabsence of film peeling. Table 1 shows the results.

Composition of Plating Solution:

Zn ion concentration 8 g/L (Zn ion source is Na₂[Zn(OH)₄])

Ni ion concentration 1.6 g/L (Ni ion source is NiSO₄·6H₂O)

caustic soda concentration 130 g/L

amine chelating agent (ethylene oxide adduct of an alkylene amine)IZ-250YB (manufactured by Dipsol) 60 g/L

brightening agent IZ-250YR1 (manufactured by Dipsol) 0.6 mL/L (polyamine0.1 g/L)

brightening agent IZ-250YR2 (manufactured by Dipsol) 0.5 mL/L (0.2 g/Lof quaternary ammonium salt of nicotinic acid)

Example 2

An anode plate (surface roughness Ra: 4 μm, 64×64×2 mm) coated withtantalum oxide in a thickness of 0.5 to 0.8 μm on Fe was used and analkaline zinc nickel alloy plating bath shown below was used (500 mL) tocarry out zinc nickel alloy plating with energizing of 500 Ah/L. Thepore diameter in the coating film was 0.1 to 1 μm, and the drag-out ofthe plating bath was set to 2 mL/Ah. The cathode current density was 4A/dm², the anode current density was 9.8 A/dm², and the plating bathtemperature was 25° C. The plating bath was cooled to maintain 25° C. Aniron plate was used as the cathode. Note that the iron plate of thecathode was replaced for each 16 Ah/L during the energizing. The zincion concentration of the plating bath was kept constant by immersion anddissolution of the metal zinc. The nickel ion concentration of theplating bath was kept constant by replenishing a nickel replenishmentagent IZ-250YNi (manufactured by Dipsol). The caustic soda concentrationof the plating bath was periodically analyzed and replenished to aconstant concentration. The brightening agents replenished werepolyamine IZ-250YR1 (manufactured by Dipsol) and nitrogen-containingheterocyclic quaternary ammonium salt IZ-250YR2 (manufactured by Dipsol)at replenishing rates of 15 mL/kAh and 15 mL/kAh, respectively. Theamine chelating agent IZ-250YB was replenished at an IZ-250YBreplenishing rate of 80 mL/kAh. The concentration of the amine chelatingagent, the oxalic acid concentration, and the cyan concentration in thecatholyte were analyzed for each energizing of 250 Ah/L. In addition,the presence or absence of precipitate was visually observed. Table 1shows the results. Moreover, the chelating agent concentration was setto the initial concentration during the energizing of 500 Ah/L and along cell having a 20 cm iron plate as the cathode was used for aplating test in accordance with the hull cell test to measure theplating appearance, the film thickness distribution, and the Nico-deposition ratio distribution. FIG. 2, FIG. 8, and FIG. 9 show therespective results. Note that the conditions for the plating test inaccordance with the hull cell test were 4A-20 minutes and 25° C. Inaddition, the surface of the anode was observed to check the presence orabsence of film peeling. Table 1 shows the results.

Composition of Plating Solution:

Zn ion concentration 8 g/L (Zn ion source is Na₂[Zn(OH)₄])

Ni ion concentration 1.6 g/L (Ni ion source is NiSO₄·6H₂O)

caustic soda concentration 130 g/L

amine chelating agent (ethylene oxide adduct of an alkylene amine)IZ-250YB (manufactured by Dipsol) 60 g/L

brightening agent IZ-250YR1 (manufactured by Dipsol) 0.6 mL/L (polyamine0.1 g/L)

brightening agent IZ-250YR2 (manufactured by Dipsol) 0.5 mL/L (0.2 g/Lof quaternary ammonium salt of nicotinic acid)

Example 3

An anode plate (surface roughness Ra: 4 μm, 64×64×2 mm) coated withtantalum oxide in a thickness of 0.5 to 0.8 μm on Ni was used and analkaline zinc nickel alloy plating bath shown below was used (500 mL) tocarry out zinc nickel alloy plating with energizing of 500 Ah/L. Thepore diameter in the coating film was 0.1 to and the drag-out of theplating bath was set to 2 mL/Ah. The cathode current density was 2A/dm², the anode current density was 4.9 A/dm², and the plating bathtemperature was 25° C. The plating bath was cooled to maintain 25° C. Aniron plate was used as the cathode. Note that the iron plate of thecathode was replaced for each 16 Ah/L during the energizing. The zincion concentration of the plating bath was kept constant by immersion anddissolution of the metal zinc. The nickel ion concentration of theplating bath was kept constant by replenishing a nickel replenishmentagent IZ-250YNi (manufactured by Dipsol). The caustic soda concentrationof the plating bath was periodically analyzed and replenished to aconstant concentration. The brightening agents replenished werepolyamine IZ-250YR1 (manufactured by Dipsol) and nitrogen-containingheterocyclic quaternary ammonium salt IZ-250YR2 (manufactured by Dipsol)at replenishing rates of 15 mL/kAh and 15 mL/kAh, respectively. Theamine chelating agent tetraethylenepentamine was replenished at areplenishing rate of 40 mL/kAh. The concentration of the amine chelatingagent and the cyan concentration in the catholyte were analyzed for eachenergizing of 250 Ah/L. In addition, the presence or absence ofprecipitate was visually observed. Table 2 shows the results. Moreover,the chelating agent concentration was set to the initial concentrationduring the energizing of 500 Ah/L and a long cell having a 20 cm ironplate as the cathode was used for a plating test in accordance with thehull cell test to measure the plating appearance, the film thicknessdistribution, and the Ni co-deposition ratio distribution. FIG. 3, FIG.10, and FIG. 11 show the respective results. Note that the conditionsfor the plating test in accordance with the hull cell test were 2A-20minutes and 25° C.

Composition of Plating Solution:

Zn ion concentration 8 g/L (Zn ion source is Na₂[Zn(OH)₄])

Ni ion concentration 1.2 g/L (Ni ion source is NiSO₄·6H₂O)

caustic soda concentration 130 g/L

amine chelating agent (tetraethylenepentamine) 30 g/L

brightening agent IZ-250YR1 (manufactured by Dipsol) 0.6 mL/L (polyamine0.1 g/L)

brightening agent IZ-250YR2 (manufactured by Dipsol) 0.5 mL/L (0.2 g/Lof quaternary ammonium salt of nicotinic acid)

Comparative Example 1

An alkaline zinc nickel alloy plating bath shown below was used (500 mL)to carry out zinc nickel alloy plating with energizing of 500 Ah/L. Thedrag-out of the plating bath was set to 2 mL/Ah. The cathode currentdensity was 4 A/dm², the anode current density was 9.8 A/dm², and theplating bath temperature was 25° C. The plating solution was cooled tomaintain 25° C. An iron plate was used as the cathode, and a nickelplate was used as the anode. Note that the iron plate of the cathode wasreplaced for each 16 Ah/L during the energizing. The zinc ionconcentration of the plating bath was kept constant by immersion anddissolution of the metal zinc. The nickel ion concentration of theplating bath was kept constant by replenishing a nickel replenishmentagent IZ-250YNi (manufactured by Dipsol). The caustic soda concentrationof the plating bath was periodically analyzed and replenished to aconstant concentration. The brightening agents replenished werepolyamine IZ-250YR1 (manufactured by Dipsol) and nitrogen-containingheterocyclic quaternary ammonium salt IZ-250YR2 (manufactured by Dipsol)at replenishing rates of 15 mL/kAh and 15 mL/kAh, respectively. Theamine chelating agent IZ-250YB was replenished at an IZ-250YBreplenishing rate of 80 mL/kAh. The concentration of the amine chelatingagent, the oxalic acid concentration, and the cyan concentration wereanalyzed for each energizing of 250 Ah/L. In addition, the presence orabsence of precipitate was visually observed. Table 1 shows the results.Moreover, the chelating agent concentration was set to the initialconcentration during the energizing of 500 Ah/L and a long cell having a20 cm iron plate as the cathode was used for a plating test inaccordance with the hull cell test to measure the plating appearance,the film thickness distribution, and the Ni co-deposition ratiodistribution. FIG. 4, FIG. 12, and FIG. 13 show the respective results.Note that the conditions for the plating test in accordance with thehull cell test were 4A-20 minutes and 25° C.

Composition of Plating Solution:

Zn ion concentration 8 g/L (Zn ion source is Na₂[Zn(OH)₄])

Ni ion concentration 1.6 g/L (Ni ion source is NiSO₄·6H₂O)

caustic soda concentration 130 g/L

amine chelating agent (ethylene oxide adduct of an alkylene amine)IZ-250YB (manufactured by Dipsol) 60 g/L

brightening agent IZ-250YR1 (manufactured by Dipsol) 0.6 mL/L (polyamine0.1 g/L)

brightening agent IZ-250YR2 (manufactured by Dipsol) 0.5 mL/L (0.2 g/Lof quaternary ammonium salt of nicotinic acid)

Comparative Example 2

An anode plate (surface roughness Ra: 4 μm, 64×64×2 mm) coated withiridium oxide in a thickness of 0.5 to 0.8 μm on Pt/Ti was used and analkaline zinc nickel alloy plating bath shown below was used (500 mL) tocarry out zinc nickel alloy plating with a energizing of 500 Ah/L. Thepore diameter in the coating film was 0.1 to 1 μm, and the drag-out ofthe plating bath was set to 2 mL/Ah. The cathode current density was 4A/dm², the anode current density was 9.8 A/dm², and the plating bathtemperature was 25° C. The plating bath was cooled to maintain 25° C. Aniron plate was used as the cathode. Note that the iron plate of thecathode was replaced for each 16 Ah/L during the energizing. The zincion concentration of the plating bath was kept constant by immersion anddissolution of the metal zinc. The nickel ion concentration of theplating bath was kept constant by replenishing a nickel replenishmentagent IZ-250YNi (manufactured by Dipsol). The caustic soda concentrationof the plating bath was periodically analyzed and replenished to aconstant concentration. The brightening agents replenished werepolyamine IZ-250YR1 (manufactured by Dipsol) and nitrogen-containingheterocyclic quaternary ammonium salt IZ-250YR2 (manufactured by Dipsol)at replenishing rates of 15 mL/kAh and 15 mL/kAh, respectively. Theamine chelating agent IZ-250YB was replenished at an IZ-250YBreplenishing rate of 80 mL/kAh. The concentration of the amine chelatingagent, the oxalic acid concentration, and the cyan concentration in thecatholyte were analyzed for each energizing of 250 Ah/L. In addition,the presence or absence of precipitate was visually observed. Table 1shows the results. Moreover, the chelating agent concentration was setto the initial concentration during the energizing of 500 Ah/L and along cell having a 20 cm iron plate as the cathode was used for aplating test in accordance with the hull cell test to measure theplating appearance, the film thickness distribution, and the Nico-deposition ratio distribution. FIG. 5, FIG. 14, and FIG. 15 show therespective results. Note that the conditions for the plating test inaccordance with the hull cell test were 4A-20 minutes and 25° C. Inaddition, the surface of the anode was observed to check the presence orabsence of film peeling. Table 1 shows the results.

Composition of Plating Solution:

Zn ion concentration 8 g/L (Zn ion source is Na₂[Zn(OH)₄])

Ni ion concentration 1.6 g/L (Ni ion source is NiSO₄·6H₂O)

caustic soda concentration 130 g/L

amine chelating agent (ethylene oxide adduct of an alkylene amine)IZ-250YB (manufactured by Dipsol) 60 g/L

brightening agent IZ-250YR1 (manufactured by Dipsol) 0.6 mL/L (polyamine0.1 g/L)

brightening agent IZ-250YR2 (manufactured by Dipsol) 0.5 mL/L (0.2 g/Lof quaternary ammonium salt of nicotinic acid)

Table 1 Transition of Concentration of Amine Chelating Agent, OxalicAcid Concentration, and Cyan Concentration as Well as Presence orAbsence of Deposits and Film Peeling

TABLE 1 Amine Energizing Chelating Oxalic Quantity Agent Acid Cyan De-Film (Ah/L) (g/L) (g/L) (mg/L) posit Peeling Initially 0 60 0 <2 None —Example 1 250 59 0.2 <2 None None 500 57 0.5 <2 None None Example 2 25058 0.3 <2 None None 500 55 0.8 <2 None None Comparative 250 40 1.7 15Yes — Example 1 500 35 2.0 30 Yes — Comparative 250 38 2.0 25 Yes YesExample 2 500 30 2.4 40 Yes Yes

Table 2 Transition of Concentration of Amine Chelating Agent and CyanConcentration as Well as Presence or Absence of Deposits

TABLE 2 Energizing Amine Chelating Quantity Agent Cyan (Ah/L) (g/L)(mg/L) Deposit Initially 0 30 <2 None Example 3 250 28 <2 None 500 27 <2None

Example 1 to 3 showed the following effects as compared with ComparativeExamples 1 and 2.

(1) The decomposition of the amine chelating agent was suppressed.(2) The lowering of the plating appearance was suppressed.(3) The decrease in plating rate was suppressed.(4) The decrease in Ni co-deposition ratio was suppressed.

The present invention made it possible to achieve lifetime extension ofan alkaline zinc or zinc alloy plating bath, particularly an alkalinezinc nickel alloy plating bath. In addition, the lifetime extension ofan alkaline zinc or zinc alloy plating bath, particularly an alkalinezinc nickel alloy plating bath made it possible to stabilize the platingquality, shorten the plating time, and reduce the burden of wastewatertreatment.

What is claimed is:
 1. A zinc or zinc alloy electroplating methodcomprising: performing energizing in an alkaline zinc or zinc alloyelectroplating bath provided with a cathode and an anode, wherein theanode is an anode in which a conductive substrate is coated in aconductive state with alkali-resistant ceramics, the alkaline zinc orzinc alloy electroplating bath is an alkaline zinc plating bathcontaining an organic compound additive or an alkaline zinc alloyelectroplating bath containing an amine chelating agent or an organiccompound additive, oxidation decomposition, on a surface of the anodecaused by the energizing, of the organic compound additive in thealkaline zinc plating bath or the amine chelating agent and the organiccompound additive in the alkaline zinc alloy electroplating bath issuppressed as compared with a case of using as an anode of the sameconductive substrate uncoated with the alkali-resistant ceramics.
 2. Thezinc or zinc alloy electroplating method according to claim 1, whereinthe anode in which a conductive substrate is coated in a conductivestate with alkali-resistant ceramics consists of a conductive substrateand an alkali-resistant ceramics coating.
 3. The zinc or zinc alloyelectroplating method according to claim 1, wherein the conductivesubstrate contains at least one of nickel and iron.
 4. The zinc or zincalloy electroplating method according to claim 1, wherein thealkali-resistant ceramics contain at least one selected from the groupconsisting of tantalum oxide, aluminum oxide, tantalum nitride, aluminumnitride, silicon nitride, boron nitride, silicon carbide, and boroncarbide.
 5. The zinc or zinc alloy electroplating method according toclaim 1, wherein the alkaline zinc or zinc alloy electroplating bath isan alkaline zinc electroplating bath at least containing zinc ions,caustic alkali, and an organic compound additive.
 6. The zinc or zincalloy electroplating method according to claim 1, wherein the alkalinezinc or zinc alloy electroplating bath is an alkaline zinc alloyelectroplating bath at least containing zinc ions, metal ions, causticalkali, an amine chelating agent, and an organic compound additive, andthe metal ions include at least one selected from the group consistingof nickel ions, iron ions, cobalt ions, tin ions, and manganese ions. 7.The zinc or zinc alloy electroplating method according to claim 6,wherein the amine chelating agent contains at least one selected fromthe group consisting of alkylene amine compounds, alkylene oxide adductsthereof, and alkanolamine compounds.
 8. A zinc or zinc alloyelectroplating system comprising: an alkaline zinc or zinc alloyelectroplating bath provided with a cathode and an anode, wherein theanode is an anode in which a conductive substrate is coated in aconductive state with alkali-resistant ceramics, the alkaline zinc orzinc alloy electroplating bath is an alkaline zinc plating bathcontaining an organic compound additive or an alkaline zinc alloyelectroplating bath containing an amine chelating agent or an organiccompound additive, oxidation decomposition, on a surface of the anodecaused by the energizing, of the organic compound additive in thealkaline zinc plating bath or the amine chelating agent and the organiccompound additive in the alkaline zinc alloy electroplating bath issuppressed as compared with a case of using as an anode of the sameconductive substrate uncoated with the alkali-resistant ceramics.
 9. Thezinc or zinc alloy electroplating system according to claim 8, whereinthe anode in which a conductive substrate is coated in a conductivestate with alkali-resistant ceramics consists of a conductive substrateand an alkali-resistant ceramics coating.
 10. The zinc or zinc alloyelectroplating system according to claim 8, wherein the conductivesubstrate contains at least one of nickel and iron.
 11. The zinc or zincalloy electroplating system according to claim 8, wherein thealkali-resistant ceramics contain at least one selected from the groupconsisting of tantalum oxide, aluminum oxide, tantalum nitride, aluminumnitride, silicon nitride, boron nitride, silicon carbide, and boroncarbide.
 12. The zinc or zinc alloy electroplating system according toclaim 8, wherein the alkaline zinc or zinc alloy electroplating bath isan alkaline zinc electroplating bath at least containing zinc ions,caustic alkali, and an organic compound additive.
 13. The zinc or zincalloy electroplating system according to claim 8, wherein the alkalinezinc or zinc alloy electroplating bath is an alkaline zinc alloyelectroplating bath at least containing zinc ions, metal ions, causticalkali, an amine chelating agent, and an organic compound additive, andthe metal ions include at least one selected from the group consistingof nickel ions, iron ions, cobalt ions, tin ions, and manganese ions.14. The zinc or zinc alloy electroplating system according to claim 13,wherein the amine chelating agent contains at least one selected fromthe group consisting of alkylene amine compounds, alkylene oxide adductsthereof, and alkanolamine compounds.